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Vaccination with Plasmodium knowlesi AMA1 formulated in the novel adjuvant co-vaccine HT™ protects against blood-stage challenge in rhesus macaques.

Mahdi Abdel Hamid M, Remarque EJ, van Duivenvoorde LM, van der Werff N, Walraven V, Faber BW, Kocken CH, Thomas AW - PLoS ONE (2011)

Bottom Line: Combined with the adjuvant CoVaccine HT™, PkAMA1 was found to be highly immunogenic in rabbits and the efficacy of the PkAMA1 was subsequently tested in a rhesus macaque blood-stage challenge model.In the PfAMA1 vaccinated control group, five out of six animals had to be treated with antimalarials 8 days after challenge; one animal did not become patent during the challenge period.This study shows that: i) Yeast-expressed PkAMA1 can protect against blood stage challenge; ii) Functional antibody levels as measured by GIA correlated inversely with the day of onset and iii) GIA IC(50) values correlated with estimated in vivo growth rates.

View Article: PubMed Central - PubMed

Affiliation: Department of Parasitology, Biomedical Primate Research Centre, Rijswijk, The Netherlands.

ABSTRACT
Plasmodium falciparum apical membrane antigen 1 (PfAMA1) is a leading blood stage vaccine candidate. Plasmodium knowlesi AMA1 (PkAMA1) was produced and purified using similar methodology as for clinical grade PfAMA1 yielding a pure, conformational intact protein. Combined with the adjuvant CoVaccine HT™, PkAMA1 was found to be highly immunogenic in rabbits and the efficacy of the PkAMA1 was subsequently tested in a rhesus macaque blood-stage challenge model. Six rhesus monkeys were vaccinated with PkAMA1 and a control group of 6 were vaccinated with PfAMA1. A total of 50 µg AMA1 was administered intramuscularly three times at 4 week intervals. One of six rhesus monkeys vaccinated with PkAMA1 was able to control parasitaemia, upon blood stage challenge with P. knowlesi H-strain. Four out of the remaining five showed a delay in parasite onset that correlated with functional antibody titres. In the PfAMA1 vaccinated control group, five out of six animals had to be treated with antimalarials 8 days after challenge; one animal did not become patent during the challenge period. Following a rest period, animals were boosted and challenged again. Four of the six rhesus monkeys vaccinated with PkAMA1 were able to control the parasitaemia, one had a delayed onset of parasitaemia and one animal was not protected, while all control animals required treatment. To confirm that the control of parasitaemia was AMA1-related, animals were allowed to recover, boosted and re-challenged with P. knowlesi Nuri strain. All control animals had to be treated with antimalarials by day 8, while five out of six PkAMA1 vaccinated animals were able to control parasitaemia. This study shows that: i) Yeast-expressed PkAMA1 can protect against blood stage challenge; ii) Functional antibody levels as measured by GIA correlated inversely with the day of onset and iii) GIA IC(50) values correlated with estimated in vivo growth rates.

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Related in: MedlinePlus

SDS-PAGE gel of vaccine antigens.SDS-PAGE gel of Pichia pastoris produced PkAMA1 DI-II-III, A non-reduced and B reduced, PkAMA1 DI-II, C non-reduced and D reduced. Lane 1, 10 µg; lane 2, 5 µg; lane 3, 2.5 µg; lane 4, 1.25 µg.
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pone-0020547-g002: SDS-PAGE gel of vaccine antigens.SDS-PAGE gel of Pichia pastoris produced PkAMA1 DI-II-III, A non-reduced and B reduced, PkAMA1 DI-II, C non-reduced and D reduced. Lane 1, 10 µg; lane 2, 5 µg; lane 3, 2.5 µg; lane 4, 1.25 µg.

Mentions: table-2-captionThe apparent molecular masses of the two constructs analyzed by 4–12% gradient SDS-PAGE were 50 kDa and 40 kDa for PkAMA1 DI-II-III and PkAMA1 DI-II respectively, in accordance with theoretical mass calculated from their respective amino acid sequences. Figure 2 shows that both products are near to apparent homogeneity. Reduction of PkAMA1 D I-II-III protein samples resulted in the appearance of two additional low molecular weight bands (Figure 2). The apparent size of the two smaller products is in accordance with the location of a proteolytic cleavage site in DII, observed in PfAMA1 FVO and 3D7 [25], [32]. Densitometric analysis of SDS-PAGE on the non-reduced samples revealed that 96% of the protein was in the main band for PkAMA1 DI-II-III and 99% for PkAMA1 DI-II. Densitometry on the reduced samples showed that less than 10% and 3% of the protein is internally cleaved, for PkAMA1 DI-II-III and PkAMA1 DI-II, respectively. Both proteins react with anti hexa-histidine antibodies, anti myc-antibodies and with the PkAMA1 specific antibody R3/1C2 (data not shown), as expected.


Vaccination with Plasmodium knowlesi AMA1 formulated in the novel adjuvant co-vaccine HT™ protects against blood-stage challenge in rhesus macaques.

Mahdi Abdel Hamid M, Remarque EJ, van Duivenvoorde LM, van der Werff N, Walraven V, Faber BW, Kocken CH, Thomas AW - PLoS ONE (2011)

SDS-PAGE gel of vaccine antigens.SDS-PAGE gel of Pichia pastoris produced PkAMA1 DI-II-III, A non-reduced and B reduced, PkAMA1 DI-II, C non-reduced and D reduced. Lane 1, 10 µg; lane 2, 5 µg; lane 3, 2.5 µg; lane 4, 1.25 µg.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3105089&req=5

pone-0020547-g002: SDS-PAGE gel of vaccine antigens.SDS-PAGE gel of Pichia pastoris produced PkAMA1 DI-II-III, A non-reduced and B reduced, PkAMA1 DI-II, C non-reduced and D reduced. Lane 1, 10 µg; lane 2, 5 µg; lane 3, 2.5 µg; lane 4, 1.25 µg.
Mentions: table-2-captionThe apparent molecular masses of the two constructs analyzed by 4–12% gradient SDS-PAGE were 50 kDa and 40 kDa for PkAMA1 DI-II-III and PkAMA1 DI-II respectively, in accordance with theoretical mass calculated from their respective amino acid sequences. Figure 2 shows that both products are near to apparent homogeneity. Reduction of PkAMA1 D I-II-III protein samples resulted in the appearance of two additional low molecular weight bands (Figure 2). The apparent size of the two smaller products is in accordance with the location of a proteolytic cleavage site in DII, observed in PfAMA1 FVO and 3D7 [25], [32]. Densitometric analysis of SDS-PAGE on the non-reduced samples revealed that 96% of the protein was in the main band for PkAMA1 DI-II-III and 99% for PkAMA1 DI-II. Densitometry on the reduced samples showed that less than 10% and 3% of the protein is internally cleaved, for PkAMA1 DI-II-III and PkAMA1 DI-II, respectively. Both proteins react with anti hexa-histidine antibodies, anti myc-antibodies and with the PkAMA1 specific antibody R3/1C2 (data not shown), as expected.

Bottom Line: Combined with the adjuvant CoVaccine HT™, PkAMA1 was found to be highly immunogenic in rabbits and the efficacy of the PkAMA1 was subsequently tested in a rhesus macaque blood-stage challenge model.In the PfAMA1 vaccinated control group, five out of six animals had to be treated with antimalarials 8 days after challenge; one animal did not become patent during the challenge period.This study shows that: i) Yeast-expressed PkAMA1 can protect against blood stage challenge; ii) Functional antibody levels as measured by GIA correlated inversely with the day of onset and iii) GIA IC(50) values correlated with estimated in vivo growth rates.

View Article: PubMed Central - PubMed

Affiliation: Department of Parasitology, Biomedical Primate Research Centre, Rijswijk, The Netherlands.

ABSTRACT
Plasmodium falciparum apical membrane antigen 1 (PfAMA1) is a leading blood stage vaccine candidate. Plasmodium knowlesi AMA1 (PkAMA1) was produced and purified using similar methodology as for clinical grade PfAMA1 yielding a pure, conformational intact protein. Combined with the adjuvant CoVaccine HT™, PkAMA1 was found to be highly immunogenic in rabbits and the efficacy of the PkAMA1 was subsequently tested in a rhesus macaque blood-stage challenge model. Six rhesus monkeys were vaccinated with PkAMA1 and a control group of 6 were vaccinated with PfAMA1. A total of 50 µg AMA1 was administered intramuscularly three times at 4 week intervals. One of six rhesus monkeys vaccinated with PkAMA1 was able to control parasitaemia, upon blood stage challenge with P. knowlesi H-strain. Four out of the remaining five showed a delay in parasite onset that correlated with functional antibody titres. In the PfAMA1 vaccinated control group, five out of six animals had to be treated with antimalarials 8 days after challenge; one animal did not become patent during the challenge period. Following a rest period, animals were boosted and challenged again. Four of the six rhesus monkeys vaccinated with PkAMA1 were able to control the parasitaemia, one had a delayed onset of parasitaemia and one animal was not protected, while all control animals required treatment. To confirm that the control of parasitaemia was AMA1-related, animals were allowed to recover, boosted and re-challenged with P. knowlesi Nuri strain. All control animals had to be treated with antimalarials by day 8, while five out of six PkAMA1 vaccinated animals were able to control parasitaemia. This study shows that: i) Yeast-expressed PkAMA1 can protect against blood stage challenge; ii) Functional antibody levels as measured by GIA correlated inversely with the day of onset and iii) GIA IC(50) values correlated with estimated in vivo growth rates.

Show MeSH
Related in: MedlinePlus